The disclosure relates to an axial piston machine as described below and to an insert part which is suitable for such an axial piston machine.
An axial piston machine is known, for example, from DE 10 2006 062 065 A1 195 36 997 C1 and datasheet RDE 93220-04-R/02.08 by Bosch Rexroth AG and can be embodied as a single or double axial piston machine and as a pump or motor. In these known solutions, the axial piston machine is embodied with a housing in which at least one cylinder drum with a multiplicity of pistons which each bound one working chamber is rotatably mounted. These pistons are each supported by means of a piston foot on a swash plate whose attitude angle determines the piston stroke.
The working chamber which is bounded in each case by a piston can be alternately connected to a high pressure duct and to a low pressure duct via a control disk which is arranged at the end of the housing. The cylinder drum is connected in a rotationally fixed fashion to a drive shaft which, depending on the type of machine (motor, pump), acts either as an output shaft or as a drive shaft.
In the abovementioned axial piston machines, the housing has a housing part which is for example pot shaped or double pot shaped and in whose pot bottom the high pressure ducts and low pressure ducts are formed, it being possible to connect said high pressure ducts and low pressure ducts in series to the working chambers of the cylinder drum via the control disk which is fixed with respect to the rotating cylinder drum. In other axial piston machines, the part of the housing in which the pressure ducts are formed can also be embodied in a plate shape.
In the control disk, a plurality of comparatively small pressure kidneys which lie on a common pitch circle and between each of which a material web is arranged are formed. On the low pressure side, each control disk is embodied with a suction kidney which extends over a circumferential angle range which is relatively large compared to the small pressure kidneys.
U.S. Pat. No. 7,257,948 B1 presents a double axial piston machine in which a charging pump which is embodied as an internally toothed gearwheel machine is arranged between two pump units. The charging pump is arranged here between two disks which are fixedly connected to the housing. The disks here have the pressure kidneys described above and a suction kidney and form at the same time the housing of the axial piston machine in this region, i.e. they are not radially surrounded by the housing or a housing part. On the drum side, each disk bears against the assigned cylinder drum.
It is disadvantageous here that the disks are not surrounded by a housing, with the result that bearing faces of the disks against the charging pump are at risk of soiling.
DE 195 36 997 C1 presents a double axial piston pump having two pump units in a swash plate configuration in which the housing has a disk-shaped central housing part in which the two drive shafts of the two units are connected to one another in a rotationally fixed fashion. An impeller wheel or impeller of a charging pump, by means of which a charging pressure can be applied for both units to the pressure medium on the low pressure side, is mounted in this region between the two shafts. In order to mount the impeller wheel, the housing part is embodied on the side of a first unit with an insert ring which is mounted after the impeller wheel is inserted into the housing part. In this insert ring, high pressure duct sections and low pressure duct sections which are assigned to the cylinder drum of the first unit are formed, said duct sections having a pressure medium conducting connection on the side of the central housing part to a high pressure duct and low pressure duct arranged in the housing part. In the second pump unit, these high pressure duct sections and low pressure duct sections are formed in the wall of the housing part.
Working chambers of the two cylinder drums can be alternately connected to the high pressure duct section and the low pressure duct section of the housing or the insert ring via a control disk which is arranged on the end side of the central housing part (second pump unit) or on the end side of the insert ring (first pump unit). In the control disk, a plurality of comparatively small pressure kidneys which are located on a common pitch circle are formed on the high pressure side, in each case a material web being arranged between said pressure kidneys. On the low pressure side, each control disk is embodied with a suction kidney which extends over a circumferential angle range which is relatively large in comparison with the small pressure kidneys.
The two control disks are of a very thin configuration here and bear with an axial bearing face, which has been ground with high precision, on a likewise precise axial bearing face of the insert ring or of the central housing part. On the drum side, the control disks are likewise fabricated and ground in a very precise spherically convex fashion.
During operation of the axial piston machine, comparatively high pressures are applied to the high pressure ducts in the central housing part, in the region of the pressure kidneys and of the material webs adjoining the latter. It is problematic here that as a rule the housing part is manufactured from ductile graphite, and that precisely in this region one zone is present which is problematic with respect to the casting front profile and in which cavity points can occur during hardening of the casting. In the case of high stresses owing to a high hydraulic pressure, damage or deformation of the housing part can then occur in the region where cavities are present, with the result that the running time of the axial piston machine is reduced.
A disadvantage of the solution is that the control disk, the insert ring and the housing part against which the control disk bears can only be fabricated at very high cost with the required precision and pressure resistance and take up a relatively large amount of space in the axial direction.
In contrast with the above, the disclosure is based on the object of providing an axial piston machine with a shortened overall length and simplified fabrication and in which the risk of damage by pressure loading is reduced.
This object is achieved by means of an axial piston machine having the features described below. The object is also achieved by an insert part having the features described below.
Further advantageous refinements of the disclosure are described below.